JimW

I was curious and wanted to see if using 87 octane would net better MPG. I have used 87 in the past a few times, but this was pre "M" flash. After putting 5 gallons of 87 I punched it to 6000 thousand RPM in 2nd gear and heard only what I can best describe as a muted sound of tiny bearings rattling around in the motor. I immediately went back to the gas station and filled up with premium as it sounds like detonation. Can this have something to do with "M" flash even though it is suppsed to run richer in this RPM band? Or is something going bad with the car such as the catylitic converter, plugs, coils, ect. I also hear what seems like a loud vacuum leak underneath the car, when I am idling and the clutch engaged. I'd be greatful for any input. Thanks.

mysql101

I ran two ranks of 87 without issue. Even a few redlines.

I'm back on 91 for the current tank as I want to make sure the engine remains clean... but I can definitely see my gas gauge go down faster with the higher oct.

Nemesis8

iTrader: (3)

I've heard this sound also around 6K - what is it?

JimW

It sounds like the car is detonating or pinging. I would sure like to take advantage of the lower octane since the manual states that it could be used, but the pinging could be and underlying problem that something else is wrong. As a matter of fact I'm pretty sure it is detonating because it is the same sound that I heard when tuning my former 20G turbo Eclipse at high boost.

JimW

Jason, 2 ranks of 87. That's hillarious, because that's what it is, RANK! Yes, I agree about running cleaner and keeping your engine intact.

PA BATMOBILE

To the pinging or detination statement. The owners manual clearly states 91+ octane. The rumor is that if you turn the DSC off-off your power and fuel will go up

JimW

No, the owners manual states that 87 octane can be used albeit at reduced power. I tried the DSC off and noticed a slight improvement in MPG although the car pulls stronger with the DSC activated in my opinion.

DreRX8

I had the same problem--the dealership went through hell to determine the issue--the cause is low octane. Eventhough I was putting 93 in--I apparently had gotten a hold of some bad gas. They filled it up with premium and the sound was gone--haven't had a problem since. So if you are running 87 octane and experience no issues-consider yourself lucky--I'll stick with 93.

zoom44

some of this may indeed be pinging but have you all read this thread and eliminated what is described there as the noise you are hearing?

stanfordcole

I'll have to check my manual again but I thought I remembered it saying the high octane(91-93) was preferred, you could run 89 with reduced performance and 87 could cause engine knocking/damage. I doubt if it causes damage but I am interested now. I will have to read that section again.

Ashah

I hear a rattling noise at exactly 3500 RPM. Has anyone heard this? Is this the same noise?

mysql101

btw, I buy my gas from brand name gas stations, never the discount quickie marts.

Maybe that is why I'm not having issues with the lower grade.

This car has always had Chevron.

Blue_Chameleon

I don't understand what is the fascination of putting in cheaper gas when it clearly state in the manual to put higher octane. Granted that gas prices are high, but it's nothing that we can do about it.

Why sacrifice the ability to save $2-$3 per fill-up just so that you can kill your engine life? I don't get it.

mysql101

The manual clearly states the 87 octane is acceptable, and will not be a problem for the car.

I happen to like going 350 miles on a tank of gas, thanks.



I've only gone two tanks on 87 so far, right now I have 91 in the tank.

zoom44

read the link in my post above that i am quoting here

Blue_Chameleon

Whoops...my error. You're right, but I did remember seeing something that shows that it's recommended to use high octane somewhere.

mysql101

Yes, they claim you may lose power if you use lower oct because the engine will retard timing and other stuff in order to prevent knocking and other engine issues.

I haven't made up my mind about it yet, but I really do like seeing 350 instead of 290 when my low light comes on.

JimW

Zoom44, That was and interesting read. Thanks for the hook-up, but I'm pretty sure it was pinging that I heard. If that sound was from the resonance intake ports switching, I would notice this no matter what octane I used. I only heard this while using 87 octane and then after I switched back to 93 the sound went away. I have to say it was extremely hot and humid out and I'm at sea level so that might have contributed along with some lousy 87 octane to the situation. Jason is right, if it states it in the manual that 87 octane is acceptable and it nets us better MPG then damit, the car shouldn't do this. After this episode I do not want to use 87 octane again, it is to risky.

mysql101

JimW, where are you buying your 87 gas from?

JimW

I wanted to get Shell but there was a problem with the lower octanes messing up the fuel guage due to and extreme amount of sulfer in the fuel, I ended up using Chevron.

mysql101

What is the build date on your car?

JimW

I do not know. Where do I find this? I am going to go outside and see if I can locate it somewhere. I'll be back in a few.

JimW

I found it. Sep 03. It was inside the door frame where the Tire psi info is.

Mag66

Interesting that the Manual says this.. as both the updated "short guide" and the 'quick tips' booklet that I got which have a print date of April 04 and May 04 respectively.. clearly state to use 91 Octane only... and not to use any lower octane gas.

JimW

My manual does not state this, nor did I get any updates about it. My car has a 2003 build date though. I can assure you I am going to use 93 from now on. I am keeping my fingers crossed, but I do not think it did any damage to the engine.